The present invention relates to an air-suspended die sorter and in particular relates to an air-suspended die sorter capable of performing die sorting, die attach and die pick-up in the semiconductor industry.
After semiconductor wafers are divided into dies, die sorters are used in manufacturing operations to pick up and place dies on die trays. The same procedure that repeats a number of times in subsequent die testing, die attach and packaging is accomplished by using die sorters.
Today""s die sorters normally attach a sorter tip to a robot arm. Having an air passage going cross its center and being connected to a vacuum pump that provides a vacuum condition, sorter tip picks up a die via suction when it approaches and reaches the die. When the robot arm carries the sorter tip to a designated location and as a proper amount of air is allowed into air passage, the die lands on the designated location since the vacuum condition no longer exists.
Since the sorter tip as described above utilizes spring type parts for providing buffer mechanism that absorbs impact energy, prior art sorter tip possesses the following deficiencies:
(1) Spring preload: Before being used as a buffer mechanism, a spring has to be preloaded with an initial compression setting, which inevitably reduces spring""s impact absorbing capacity. This reduction of capacity causes damage to the die if and when the sorter tip fails to provide adequate impact absorbance.
(2) Mechanical friction: A spring has to overcome mechanical friction when being used to provide a buffer mechanism. This further reduces spring""s impact absorbing capacity.
(3) Difficulties in picking up the die: When the spring type sorter tip fails to provide adequate impact absorbance, small dies (less than 0.5 cm2, for example) often get flipped over or get damaged by a spring type sorter.
(4) Imprecise control: Prior art spring type sorter tip is incapable of controlling the amount of air that is allowed in to break the vacuum condition. This lack of precision control often causes the die to land too fast such that the die flips over, stands up on its side or lands outside die tray. Sometimes, the die fails to land at all.
Aimed at resolving the above disadvantages, the main object of the present invention is to provide an air-suspended die sorter capable of eliminating spring preload, lowering mechanical friction so as to lift die sorting precision and elevate success rate.
Another object of the present invention is to provide an air-suspended die sorter capable of controlling and providing the precise amount of air by solenoid valves and pneumatic regulators to terminate the vacuum state, thus raising the success rate for landing the die.
In order to attain the above goals, an air-suspended die sorter 10 in accordance with the first preferred embodiment of the present invention comprises a cylinder unit, a piston unit and a pressure unit. The cylinder unit includes at least a trunk and a lower cap. The trunk has a through hole going through it and said through hole has a first end and a second end. Located on the side of the second end of the trunk, the lower cap and the trunk form a hollow space therein between. A first fitting and a second fitting are provided on the trunk such that the first fitting is connected with the first end of the through hole and the second fitting is connected with the hollow space. The piston unit includes at least one shank holder shaft. The shank holder shaft comprises a piston portion, an air-suspended portion, an extension portion and an air passage going through the piston portion, the air-suspended portion and the extension portion. The piston portion is capable of fitting in the through hole and moving along the axis. A first air chamber is formed between the air-suspended portion, which is provided in the hollow space, and the trunk. The extension portion extends outside the lower cap through a gap provided between the lower cap and the extension portion. The pressure unit includes at least a vacuum device, a pressure source and a first pneumatic regulator. Being connected with the first fitting, the vacuum device is capable of providing a low-pressure state at the first end of the through hole and the air passage for enabling the pick-up operation. Being connected between the second fitting and the pressure source, the first pneumatic regulator is capable of controlling the pressure in the sealed first chamber and balancing the pressure on the top and on the bottom of the air-suspended portion, thereby providing the air-suspended state for the shank holder shaft.
The pressure unit further includes a first solenoid valve, a second solenoid valve and a second pneumatic regulator. The first solenoid valve is connected between the vacuum device and the first fitting. One end of the second solenoid valve is connected with the first solenoid. The second pneumatic regulator is connected between the second solenoid valve and the pressure source. By properly controlling the first solenoid valve and the second solenoid valve to switch between having air flow and otherwise, the pressure source provides a certain amount of air between the first solenoid valve and the second solenoid valve. The first solenoid valve allows the first fitting to be in air contact with the vacuum device and the second solenoid valve, alternatively. When the first fitting is in air contact with the vacuum device, the air passage that goes through the pick-up tip, the pick-up head and the piston, respectively, is in a low-pressure state (or vacuum state) for allowing a die to be picked up. When the first fitting is having air contact with the second solenoid valve, said certain amount of air between the first solenoid valve and the second solenoid valve is permitted to enter the air passage and terminate the vacuum condition, thereby allowing a die to be released.
Thank to a piston type design and a precise control of pressure on the top and on the bottom of the piston, respectively, the present invention offers an air-suspended state that has done away with stress problems associated with using springs. The present invention further provides a novel buffer design for reducing friction and die impact often encountered in prior art applications. Precise amount of air is sealed between the solenoid valves by serially connecting the piston type die sorter with two solenoid valves and a pneumatic regulator. Moreover, termination of vacuum state is accomplished by allowing the precise amount of air sealed between the two solenoid valves to enter the air-suspended die sorter.
The following Description and Designation of Drawings are provided in order to help understand the features and content of the present invention.